1. Field of the Invention
The present invention relates to a slurry to be used for CMP (Chemical Mechanical Polishing), a polishing method using the slurry, and a method of manufacturing a semiconductor device.
2. Description of the Related Art
It is expected that the integration of semiconductor elements in high performance LSIs of the next generation would be inevitably further enhanced. For example, the design rule of damascene wirings to be formed by CMP is expected to become so severe that the line width of wirings is confined within the range of 0.07 to 30 μm and the film thickness of wirings is confined to 100 nm or less. In the manufacture of such high performance LSIs, the magnitude of dishing to be generated on the occasion of CMP is required to be suppressed to 30 nm or less.
In the formation of Cu damascene wirings, a Cu film is ordinary deposited by a process employing plating. Due to the characteristics of plating, it is impossible to deposit the Cu film with uniform film thickness, so that in a region where a wiring trench having a width of 0.07 μm is arranged at a high density (coverage ratio: 50%), the Cu film is deposited thickly because of over-plating. In the region other than the aforementioned region, for example in the region where a wiring trench having a width of 30 μm is formed, a Cu film is deposited up to a film thickness reflecting the projected/recessed surface of underlying substrate. On the occasion of flattening the surface of the Cu film deposited in this manner by CMP, it is required, for the purpose of avoiding the short circuit of wirings, to prevent as much as possible the residue of Cu in the region of over-plating. At the same time, it is also required, in the regions other than that of over-plating, to suppress the magnitude of dishing to 30 nm or less.
With a view to minimize the dishing and scratch and to polish the Cu film at a high polishing rate, there has been proposed a slurry containing a first surfactant which is capable of interacting with Cu and a second surfactant which is incapable of interacting with Cu. In this case, the residue of Cu in the aforementioned region of over-plating would be about 33 nm for example (in the case of CuCMP, an over-polish of just+30%). On the other hand, the dishing in the region of 30 μm wirings would be 30 nm or so.
With a view to further enhance the hydrophilicity of a Cu surface-protecting film, there has been proposed a slurry containing two kinds of heterocyclic compounds. In this case, the residual Cu film in the aforementioned region of over-plating can be improved up to 15 nm or so (in the case of CuCMP, an over-polish of just+30%). In the region of 30 μm wirings, the dishing can be reduced to 25 nm or so.
With a view to enhance the polishing rate of Cu, there has been proposed a slurry containing chelate resin particles and inorganic particles. In this case, the ratio in particle size between the resin particle and the inorganic particle is 30 or more. Namely, it is impossible, with employment of this slurry, to suppress the dishing and to improve the residual Cu in the region of over-plating.
In the CMP of next generation, it is now desired that in the region where the width of wirings is set to 0.07 μm and the coverage ratio is set to 50%, the residual Cu after CMP should be confined to 2 nm or less, and in the region where the width of wirings is set to 30 μm, the dishing should be suppressed to 30 nm or less. At present however, it is considered very difficult to achieve these desirable features.